Implementation and Analyzing the Grell-Freitas Convective Parameterization in The NOAA Environmental Modeling System-Based Global Spectral Model

Following the concept of Arakawa et al. (2011) to build a unified convective parameterization for use at all horizontal scales, Grell and Freitas (GF, 2014) introduced a scale-aware approach into a pre-existing scheme based on a stochastic approach. Development and testing of the GF parameterization are partially supported by the National Weather Service Research to Operations initiative. Interest in this scheme by Environmental Modeling Center (EMC) and the Next Generation Global Prediction System (NGGPS) Program Office has led to the implementation and testing for potential use in the NCEP operational global model. We implemented the GF parameterization in a developmental version of the NOAA Environmental Modeling System (NEMS)-based Global Spectral Model (GSM), and ran experimental retrospective forecasts using the NEMS-GSM over a warm (June, July, August 2015) and cool (December 2015, January, February 2016) season.

For statistical verification of the full time period of forecasts run, the audience is referred to the companion paper by Harrold et al. in this conference. In this study, focus is placed on the physical interpretation of the statistical verification with a few cases selected from the retrospective forecasts. In depth analysis of the impact of convective parameterization on surface precipitation and other fields of interest will be performed. The goal of these analyses is to learn the strength and weakness, and improve the scheme in collaboration with the GF developers.  Special attention will be given to the partition of convective versus grid scale precipitation, and to the distribution of total precipitation over land and ocean.  This work is performed by the Global Model Test Bed (GMTB), a new entity formed within the Developmental Testbed Center in 2015 to support transition of research to operations for the NCEP global model development under the auspices of NGGPS.